The answer, as pointed out above, is that the compiled modules cannot be shared.

What I ended up doing was passing PREFIX=~/perl to the initial config program and also to CPAN. This has lead to a completely separate install for the threaded perl.

As a convenience I have linked /usr/local/bin/tperl to /home/evdb/perl/bin/perl so that it is easy in scripts to change the perl version that is used.

Pity that DBI doesn't trust itself with threads, it rather removed the point of having them for me, I'll go the trusty forking route instead....

Oh, I was running 5.8.0, 5.6.1 indeed!

--tidiness is the memory loss of environmental mnemonics